x86: ivybridge: Only run the Video BIOS when video is enabled

x86: ivybridge: Only run the Video BIOS when video is enabled

This takes about about 700ms on link when running natively and 900ms when
running using the emulator. It is a waste of time if video is not enabled,
so don't bother running the video BIOS in that case.

We could add a command to run the video BIOS later when needed, but this is
not considered at present.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>